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How to remove a field completely from a MongoDB document?

{ 
    name: 'book',
    tags: {
        words: ['abc','123'],
        lat: 33,
        long: 22
    }
}

Suppose this is a document. How do I remove "words" completely from all the documents in this collection? I want all documents to be without "words":

 { 
     name: 'book',
     tags: {
         lat: 33,
         long: 22
     }
}

X
Xavier Guihot

Try this: If your collection was 'example'

db.example.update({}, {$unset: {words:1}}, false, true);

Refer this:

http://www.mongodb.org/display/DOCS/Updating#Updating-%24unset

UPDATE:

The above link no longer covers '$unset'ing. Be sure to add {multi: true} if you want to remove this field from all of the documents in the collection; otherwise, it will only remove it from the first document it finds that matches. See this for updated documentation:

https://docs.mongodb.com/manual/reference/operator/update/unset/

Example:

db.example.update({}, {$unset: {words:1}} , {multi: true});

See the solution to this question for explanation of false/true stackoverflow.com/questions/7714216/…
There's no longer a comment by a "Nic Cottrell" anywhere on this page :)
Am I missing something, or has this been wrong for 8+ years, because tags.words should be $unset, not words? See also Salvador Dali's answer.
You can also use updateMany instead of {multi:true}, i.e. db.example.updateMany({},{"$unset":{words:""}})
Why do people keep the old code, which does not work, in the updated answer? I assume people come here to look for answers and not scroll down, read complete answer to figured it out the way it was before in 10 years ago. This is very common in SO.
S
Suman Kundu

In the beginning, I did not get why the question has a bounty (I thought that the question has a nice answer and there is nothing to add), but then I noticed that the answer which was accepted and upvoted 15 times was actually wrong!

Yes, you have to use $unset operator, but this unset is going to remove the words key which does not exist for a document for a collection. So basically it will do nothing.

So you need to tell Mongo to look in the document tags and then in the words using dot notation. So the correct query is.

db.example.update(
  {},
  { $unset: {'tags.words':1}},
  false, true
)

Just for the sake of completion, I will refer to another way of doing it, which is much worse, but this way you can change the field with any custom code (even based on another field from this document).


Addition to this, if tags is an array then it would be like this: db.example.update({},{ $unset: {'tags.$[].words':1}},false, true)
V
Vipul Pandey
db.example.updateMany({},{"$unset":{"tags.words":1}})

We can also use this to update multiple documents.


i find this clearer than passing false, true as last two args to update()
s
shA.t

To remove or delete field in MongoDB

For single Record db.getCollection('userData').update({}, {$unset: {pi: 1}})

For Multi Record db.getCollection('userData').update({}, {$unset: {pi: 1}}, {multi: true})


J
Julian Rex
db.collection.updateMany({}, {$unset: {"fieldName": ""}})

updateMany requires a matching condition for each document, since we are passing {} it is always true. And the second argument uses $unset operator to remove the required field in each document.


X
Xavier Guihot

Starting in Mongo 4.2, it's also possible to use a slightly different syntax:

// { name: "book", tags: { words: ["abc", "123"], lat: 33, long: 22 } }
db.collection.updateMany({}, [{ $unset: ["tags.words"] }])
// { name: "book", tags: { lat: 33, long: 22 } }

Since the update method can accept an aggregation pipeline (note the squared brackets signifying the use of an aggregation pipeline), it means the $unset operator used here is the aggregation one (as opposed to the "query" one), whose syntax takes an array of fields.


Y
Yakir Tsuberi

The solution for PyMongo (Python mongo):

db.example.update({}, {'$unset': {'tags.words':1}}, multi=True);

J
Jonathon Gardner

I was trying to do something similar to this but instead remove the column from an embedded document. It took me a while to find a solution and this was the first post I came across so I thought I would post this here for anyone else trying to do the same.

So lets say instead your data looks like this:

{ 
  name: 'book',
  tags: [
    {
      words: ['abc','123'],
      lat: 33,
      long: 22
    }, {
      words: ['def','456'],
      lat: 44,
      long: 33
    }
  ]
}

To remove the column words from the embedded document, do this:

db.example.update(
  {'tags': {'$exists': true}},
  { $unset: {'tags.$[].words': 1}},
  {multi: true}
)

or using the updateMany

db.example.updateMany(
  {'tags': {'$exists': true}},
  { $unset: {'tags.$[].words': 1}}
)

The $unset will only edit it if the value exists but it will not do a safe navigation (it wont check if tags exists first) so the exists is needed on the embedded document.

This uses the all positional operator ($[]) which was introduced in version 3.6


This answer needs to be upvoted more, but I guess it's difficult to compete with answers that are 6 years older.
M
Mathieu Dhondt

Because I kept finding this page when looking for a way to remove a field using MongoEngine, I guess it might be helpful to post the MongoEngine way here too:

Example.objects.all().update(unset__tags__words=1)

V
Vince

In mongoDB shell this code might be helpful:

db.collection.update({}, {$unset: {fieldname: ""}} )

A
Amitesh Bharti

By default, the update() method updates a single document. Set the Multi Parameter to update all documents that match the query criteria.

Changed in version 3.6. Syntax :

db.collection.update(
   <query>,
   <update>,
   {
     upsert: <boolean>,
     multi: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ]
   }
)

Example :

db.getCollection('products').update({},{$unset: {translate:1, qordoba_translation_version:1}}, {multi: true})

In your example :

db.getCollection('products').update({},{$unset: {'tags.words' :1}},  {multi: true})

J
Jon Kern

And for mongomapper,

Document: Shutoff

Field to remove: shutoff_type

Shutoff.collection.update( {}, { '$unset' => { 'shutoff_type': 1 } }, :multi => true )


K
Kaveh Naseri

To Remove a field you can use this command(this will be applied to all the documents in the collection) :

db.getCollection('example').update({}, {$unset: {Words:1}, {multi: true});

And to remove multiple fields in one command :

db.getCollection('example').update({}, {$unset: {Words:1 ,Sentences:1}}, {multi: true});

P
Poonam Agrawal

{ name: 'book', tags: { words: ['abc','123'], lat: 33, long: 22 } }

Ans:

db.tablename.remove({'tags.words':['abc','123']})


A
Abhi

Checking if "words" exists and then removing from the document

    db.users.update({"tags.words" :{$exists: true}},
                                           {$unset:{"tags.words":1}},false,true);

true indicates update multiple documents if matched.


You don't need to check for existence. The documentation states that :"If the field does not exist, then $unset does nothing (i.e. no operation)."
j
joel Raja

you can also do this in aggregation by using project at 3.4

{$project: {"tags.words": 0} }


t
taskinoor

To reference a package and remove various "keys", try this

db['name1.name2.name3.Properties'].remove([
{
     "key" : "name_key1"
},
{
     "key" : "name_key2"
},
{
     "key" : "name_key3"
}
)]